The drain plug for crankcases of most internal combustion engines as described in U.S. Pat. No. 3,874,478 is essentially the same as the drain plugs of the first internal combustion engines. While the standard drain plug remains inexpensive to make and to install, the problems of changing the oil are well documented in U.S. Pat. No. 3,874,478. Several attempts have been made to replace the standard drain plug but thus far engine manufacturers have retained the plug in its original form. In 1937, Hackel, U.S. Pat. No. 2,095,696 provided a transversely mounted cylindrical plug biased to a closed position by a compression spring. The Hackel drainage device can be held in the open position but the many parts render the device prohibitively expensive. In 1953, Gerhard, U.S. Pat. No. 2,657,705 taught the use of a remotely controllable crankcase drain valve using a reciprocating slide valve closeable by a compression spring. Again, the Gerhard device was apparently too complex and expensive for general adoption.
In 1962, Montague U.S. Pat. No. 3,049,334 presented a drain valve and extension tool for removing used oil from the crankcase without the necessity of crawling under the car. The Montague device is relatively simple and consists of a hollow valve stem with external threads and a radial opening. The Montague valve could separate from the valve housing and drop into a used oil receiver if unthreaded too far resulting in a vexatious retrieval problem.
Schramm received U.S. Pat. No. 3,677,369 in 1972 on a unique ball valve to be used in draining used crankcase oil. The tolerances on such valves are critical and machining would be expensive.
Mantell, in U.S. Pat. No. 3,874,478 granted in 1975 provides a removable tapered plug in a special crankcase drain plug assembly. The plug is held in place by a spring clip, both of which could be lost or mislaid during an oil change.
Tibbitts was granted U.S. Pat. No. 4,025,048 on May 24, 1977 for a drain plug assembly. There are no parts which can become separated from the assembly during use but there are a number of parts which must be machined and several threaded parts, resulting in a costly device.
The most recent drain device for oil pans known to Applicant is Mitsui, U.S. Pat. No. 4,086,981 granted May 2, 1978. The Mitsui device includes a slide valve which is remotely operated and requires a compression spring to return the valve to a closed position. There are many parts and the device is obviously quite expensive.